How Does a 16 Million Color E-Paper Work?

October 10, 2023
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From mobile phones and tablets to big-screen TVs and digital signage, we live in a world filled with color screens, providing us with high-definition, vivid entertainment all the time.

As extreme weather events occur more frequently, countries around the world are setting carbon-neutral goals to combat climate change. We need more energy-saving and environmentally friendly displays to replace the power-hungry and high-emission LCD screens. So color e-paper is becoming the next big thing in making displays greener.

What is a color e-paper?

Color e-paper is a bistable color display that doesn't require power to stay active, but only uses energy to update the screen. This has significant power-saving advantages over traditional LCD screens.

Image with red, yellow, and blue primary colors
Color e-paper is a full-color display with low power consumption.

E-papers form images by reflecting ambient light, which is different from light-emitting LCDs, so e-papers are easily readable under direct sunlight and do not emit blue light harmful to the eyes.

How does color e-paper work?

The most popular e-paper technologies on the market are electrophoretic (EPD) and cholesteric LCD (ChLCD).

EPD e-paper technology arranges charged ink capsules to create pixels, it is the most popular technology in black-and-white e-book readers. EPD mixes 4 ink colors or uses color filters to create around 4,000 colors at the most, which is a long way from the 16 million colors displayed on LCDs created by mixing 256 levels each of red, green, and blue. This makes it difficult for EPD e-paper displays to replace LCDs in practice.

Diagram of color E-paper formation principle
EPD e-paper uses charged ink capsules to create pixels.

IRIS Optronics uses 3 layers of ChLCD, each representing red, green, and blue, and has the bistable nature that exists between the two stable states:

  • The planar state has the liquid crystal particles lined up uniformly to reflect specific wavelengths of light, to form unique colors.
  • The focal conic state lines up the liquid crystal particles in a way to let light pass through, displaying the colors underneath.
ChLCD wavelength segment visible to the human eye
Altering the ChLCD particles on different layers to fully reflect light (white), partial reflection (gray), or no reflection (black).

By changing the 3 ChLCDs individually, we can display more than 16.78 million vibrant colors. It is the key color e-paper technology to replace light-emitting LCD and LED displays.

Advantages of color e-paper

Advantages of color e-paper displays include:

  • Energy-saving and green - color e-paper only consumes power when refreshing the screen. In an update frequency of every 5 minutes, the e-paper display only requires 1% of the power used by an LCD. So e-paper displays have a very low carbon footprint.
  • Eye care - unlike an LCD that actively emits light, including blue light, to display, e-paper reflects ambient light to form images, making it a more comfortable reading medium.
  • Sunlight readable - unlike an LCD that needs to increase brightness to be legible in the sun, an e-paper display can provide vivid images by reflecting the sunlight, making it ideal for outdoor signage applications.
  • Solar integration - while the ChLCD reflects different wavelengths of light, around 10-30% of the light passes through the display. By embedding solar cells under the screen, we create the Infinity Display that generates renewable energy to power itself.
Infinity Display trichromatic light wavelength principle
Use solar cells to replace the backsheet of the ChLCD to generate electricity from ambient light.

Color e-paper applications

The environmentally friendly color e-paper has many applications to reduce energy consumption and carbon footprint:

  • Public Transport - the green e-paper display is clearly visible in direct sunlight, and is very suitable for providing a low power consumption display outdoors, which can interact with the cloud to update real-time traffic information.
  • Smart education - the reflective color e-paper can significantly cut down on the blue light damage to our eyes and provide a more comfortable reading environment. It combines with ebooks to reduce paper use, eliminate the heavy books to carry to school and reduce power consumption and carbon emission.
  • Smart retail - the e-paper can be self-powered by solar energy to be untethered from the power grid, and display full-color digital posters anywhere outdoors. It can also work as a low-emission smart menu display indoors.
  • Smart healthcare - an environmentally friendly, low emission smart display combined with a digital database to provide more accurate and up-to-date health records. The touch screen can synchronize data with the cloud to improve diagnosis efficiency and eliminate mistakes.

If you would like to know more about color e-paper applications, please get in touch with us.